Audi A3 Brake Bleeding. HELP!

[Ryan12345]

Today I changed the brake master cylinder on my A3 because the brake pedal occasionally went to the floor. The brake fluid was black, so assumed it must have been the seals in the master cylinder. After changing, I bled the brakes in the normal way, started with the O/S/R wheel, then N/S/R, then N/S/F then O/S/F. However no matter how hard I try, I cannot get a good pedal. Am I missing something???

[Magnet]

Hello Ryan,

Sorry to hear of your problem. 
Are you now getting clear fluid coming through all bleed nipples? 

If so, you could try finding  yourself an interested accomplice who can pump the brake pedal until it’s as hard as he/she can get it, and at that exact point you open the bleed nipple on that wheel. 
Top up the master cylinder and repeat this procedure at each wheel. See if that improves your pedal. It could be advantageous to have the engine running to gain the servo assistance. Please obverse all safety requirements. 
If this procedure makes a noticeable improvement, then I would repeat it until you are happy. 

If it doesn’t get you to where you want to be, then it would be a case of getting the system pressure - or vacuum bled. 
Perhaps you could let us know how you get on. 
Kind regards,

Gareth. 

[Ryan12345]

Hi, thanks for the reply. I am getting clear fluid, no air bubbles. I have tried undoing the nipple and letting it bleed itself as well as having an assistant to pressure the brakes as I undo and do up the nipple, which also has not helped. Really struggling as to what to try next. 

Thanks

[Stagn8]

Just confirming, if your aren’t using a one way kit or having the end of the bleed hose in fluid, then you need to lock off nipple with brake pedal on the floor, this ensures nothing untoward (air) gets sucked back in.

Gareth gives good advice and the only other thing I can suggest is the master cylinder isn’t fully bleeding giving you the soft pedal or there is a regulator or similar in the brake lines holding a bit of air. Try tracking your brake lines from each wheel back to the master cylinder looking for anything that might interrupt flow.

[Ryan12345]

Hi, I have a proper brake bleedng tub with pipe and one way valve. I have just tried bleeding on each individual pipe on the ABS unit, to no avail. I have also blanked off the pipes from the master cylinder and the pedal goes rock hard so mushmt be from the ABS unit onwards. Thanks

[Magnet]

Hello Ryan, 

Many thanks. It’s always useful to know what has been tried, to avoid duplication of advice, and I feel that combining what we now know you have indeed done, with Keith and my comments, points you towards needing some assistance via. the use of the more the professional equipment I mentioned. 
Just one point :- personally, I’m not a great fan of the one way valve bleeding tubes, preferring the end of the tube to be immersed in a jar with brake fluid. 
Kind regards,

Gareth. 

[Stagn8]

I guess you may have gone as far as you can with your current equipment, as Gareth mentions it is more common now to use a vacuum system or more cheaply pumping fluid from each wheel cylinder back to the master cylinder pushing any air on its way. The kits for DIY are reasonably priced but a bit ‘low rent’.

[cliffcoggin]

The calipers on some cars have two bleed nipples. I don't know if the A3 does as my manual is not to hand, but it is worth looking.

[Spock]

Could be air trapped in the ABS unit . On some cars you have to force the ABS unit to operate to bleed the air out of it . May be worth researching and finding someone with VW software